Modular computer system mechanical interconnection

ABSTRACT

A modular computer system mechanical interconnection includes a primary chassis having a first opening and a secondary chassis attached to the primary chassis and having a second opening, wherein the first opening and the second opening are generally aligned. The apparatus further includes a backplate covering the aligned first opening and second opening.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to expanding the capabilities ofa computer system, and, more particularly, to interfacing an externalmodule with a primary module of a computer system.

[0003] 2. Description of the Related Art

[0004] Historically, computer systems are general purpose devices thatmay be modified to perform particular tasks or functions. Generally,computer systems include a motherboard mounted in a cabinet. Themotherboard typically includes a number of connectors or slots in whichspecial purpose printed circuit boards may be inserted. These specialpurpose printed circuit boards may be used to add to or enhance thefunctionality of the computer system. For example, a conventionalcomputer system may have its graphics capability enhanced by theaddition of a graphics card. Similarly, the sound-producing capabilityof the computer system may be enhanced by the addition of a sound card.

[0005] One limitation on the ability to add to or enhance thefunctionality of the computer system is the number of slots orconnectors that are provided. For example, if a user desires to enhanceboth sound and graphics capability, but only a single slot or connectoris available, then the user must select the more desirable function oralternate between the cards, as needed. Neither solution is particularlydesirable.

[0006] In some computer systems, additional functionality is provided onthe motherboard itself. That is, the motherboard may be designed withelectrical leads or traces formed therein to provide interconnectivityto a special-purpose circuit. The integrated circuits used to performthe functionality of the special-purpose circuit may only be included onselect motherboards where the customer has ordered the special-purposecircuit. Typically, this approach is used so that a manufacturer maydesign a single motherboard that is used in a variety of computersystems to achieve economies of scale in manufacturing the motherboard.However, the real estate on the motherboard is “wasted” in thosecomputer systems that do not use the special purpose circuit. Forexample, it may be desirable to have additional microprocessors toprovide a high-end computer system capable of performing more intenseprocessing in some applications. Thus, the motherboard may be designedto accept multiple microprocessors, but only a single microprocessor isactually placed in the motherboard unless the customer requestsadditional microprocessors. Thus, in those systems in which only asingle microprocessor is installed, valuable motherboard real estate isunused and performing no useful work for the computer system.

[0007] Some prior devices have suggested adding or enhancingfunctionality through an external connection to the computer system.This solution suffers from a variety of mechanical and electricalchallenges, such as providing secure and high-quality electricalconnections, difficulty of assembly, electromagnetic interference,cooling, and the like. Additionally, for these external or secondarydevices to operate efficiently, they need to have a high-speedconnection to the computer system, such as through a peripheralcomponent interface (PCI) bus, an industry standard architecture (ISA)bus, a proprietary bus, a system bus, or the like. Extending ahigh-speed bus external to the cabinet of the computer system can createsubstantial difficulties. For example, a high-speed bus is sensitive tothe length of the traces used to form the bus. Extending the bus will,of course, change the length of the traces, creating the potential forreflections and other interference anomalies on the extended bus.Further, timing difficulties may also arise from the extended distancethat the signals must travel on the extended bus.

[0008] While minimizing the length of the high-speed bus extension ishelpful in minimizing these electrical problems, it creates problems forphysically connecting the components of the computer system to oneanother. For example, if the components to be interconnected are notphysically aligned, a connection between the components may beimpossible. If a connection can be physically accomplished, forcesacting on the components due to misalignment may result in mechanicalfailure of one or more of the components, either immediately or at somefuture time. Such stress in these components can cause traces to crackand fail, solder joints to become loosened, and board-level devices tofail.

[0009] The present invention is directed to overcoming, or at leastreducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE INVENTION

[0010] In one aspect of the present invention, a modular computer systemmechanical interconnection is provided. The apparatus includes a primarychassis having a first opening and a secondary chassis attached to theprimary chassis and having a second opening, wherein the first openingand the second opening are generally aligned. The modular computersystem further includes a backplate covering the aligned first openingand second opening.

[0011] In another aspect of the present invention, a modular computersystem is provided. A modular computer system includes a primary chassishaving a first opening, a motherboard disposed in the primary chassis,wherein the motherboard has an electrical connector disposed behind thefirst opening, and a secondary chassis attached to the primary chassisand having a second opening, wherein the first opening and the secondopening are generally aligned. The modular computer system furtherincludes an external device disposed in the secondary chassis, whereinthe external device has an electrical connector disposed behind thesecond opening. Further, the system includes a bridgeboard having afirst electrical connector interconnected with the motherboardelectrical connector and a second electrical connector interconnectedwith the external device connector, wherein the bridgeboard is disposedwithin the aligned first opening and second opening, and a backplatecovering the aligned first opening and second opening.

[0012] In yet another aspect of the present invention, an apparatus forelectrically interconnecting a first device with a second device isprovided. The apparatus includes a first connector, a flexible circuitelectrically connected to the first device and the first connector, anda second connector electrically connected to the second device. Theapparatus further includes a guide pin attached to a structure that isattached to the first device and a guide block having a recesstherethrough and attached to the first connector, wherein the recess isadapted to receive the guide pin so that the guide block is capable ofsliding along the guide pin.

[0013] In a further aspect of the present invention, an apparatus forelectrically interconnecting a first device with a second device. Theapparatus includes a first connector electrically connected to the firstdevice, a second connector, and a connector board attached to andelectrically connected to the second connector. The apparatus furtherincludes a flexible circuit electrically connected to the second deviceand the connector board, a guide pin attached to a structure that isattached to the second device, and a guide block having a recesstherethrough and attached to the connector board, wherein the recess isadapted to receive the guide pin so that the guide block is capable ofsliding along the guide pin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich the leftmost significant digit(s) in the reference numeralsdenote(s) the first figure in which the respective reference numeralsappear, and in which:

[0015]FIG. 1 is a block diagram of an embodiment according to thepresent invention;

[0016]FIG. 2 is a stylized representation of a bridgeboard according tothe present invention;

[0017]FIG. 3 is a stylized representation of a motherboard used inconjunction with the present invention;

[0018]FIG. 4 illustrates a datum structure for the motherboard shown inFIG. 3;

[0019]FIG. 5 is an exploded perspective view of a computer systemaccording to the present invention;

[0020]FIG. 6 is a perspective view of the computer system shown in FIG.5;

[0021]FIG. 7 is a perspective view of the computer system shown in FIGS.5 and 6;

[0022]FIGS. 8A and 8B illustrate representations of the motherboard andexternal device interconnections with the bridgeboard according to anembodiment of the present invention;

[0023]FIG. 9 illustrates representations of the motherboardinterconnection with the bridgeboard according to another embodiment ofthe present invention; and

[0024]FIG. 10 illustrates representations of the motherboardinterconnection with the bridgeboard according to a further embodimentof the present invention.

[0025] While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but, on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0026] Illustrative embodiments of the invention are described below. Inthe interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

[0027] Referring to FIG. 1, a computer system according to the presentinvention includes a primary device, e.g., a motherboard 100, containedwithin a primary chassis 105 and at least one external device 110contained within a secondary chassis 115. Although only one externaldevice 110 is shown in FIG. 1 and described herein, the scope of thepresent invention includes the use of any number of external devices110. The high-speed bus of the motherboard 100 and the high-speed bus ofthe external device 110 are directly interconnected by a bus 120, whichcarries high-speed transmissions between the motherboard 100 and theexternal device 110. Thus, electrical signals carried on the bus of themotherboard 100 are transmitted to the bus of the external device 110,and the electrical signals carried on the bus of the external device 110are transmitted to the bus of the motherboard 100. The motherboard 100and the external device 110 may, however, communicate at differentspeeds or at relatively the same speed.

[0028] Such high-speed communications are highly affected by distancesover which the communications must travel. Longer electrical paths ortraces result in slower transmission times; conversely, shorterelectrical paths result in faster transmission times. Further, variousexternal devices, such as the external device 110, typically do notoperate according to the same protocol as motherboards, such as themotherboard 100. The present invention addresses these problems byproviding a bus 120 that is short, so as to minimize impact tocommunication speed, and that has a bridge chip 125 to electricallybridge between various communication speeds, protocols, and otherenvironments. Thus, the external device 110 can be any desired device,e.g., storage media, a sound processor, a graphics processor, etc.Further, the external device 110 may communicate at any speed, faster orslower, relative to the motherboard 100 and may communicate with anyprotocol. Thus, the bridge chip 125 is capable of receiving signals frombus of the primary device (e.g., motherboard 100) and repeating thesignals over the bus of the external device 110. Further, the bridgechip 125 is capable of receiving signals from the bus of the externaldevice 110 and repeating the signals over the bus of the primary device(e.g., motherboard 100). The bridge chip 125 can receive the signals ata first transmission speed and retransmit them at a second transmissionspeed. Further, the bridge chip 125 can receive the signals under afirst signal protocol and retransmit the signals under a second signalprotocol. The bridge chip 125 creates a bridge between the environmentof the motherboard 100 and the environment of the external device 110without taxing performance of either the motherboard 100 or the externaldevice 110.

[0029] Further, the primary chassis 105 and the secondary chassis 115comprise aspects that minimize the possibility of electromagnetic wavesfrom being radiated beyond the chassis 105, 115 from the electroniccomponents therein. Such radiated waves can cause electromagneticinterference (EMI) in other devices. As it is possible for suchelectromagnetic waves to be radiated from the bus 120, one aspect of thepresent invention provides EMI shielding 130 for the bus 120.

[0030] The illustrated embodiment provides separate power supplies 135,145 for providing power to each of the motherboard 100 and the externaldevice 110, respectively. The illustrated embodiment further providesseparate cooling devices 140, 150 for each of the primary chassis 105and the secondary chassis 115, respectively. These cooling devices 140,150 provide cooling to the motherboard 100 and the external device 110and to other devices, if present, in the chassis 105, 115.

[0031] In one embodiment of the present invention, the motherboard 100is connected to the external device 110 via a bridgeboard 200, which isshown in a stylized fashion in FIG. 2. Generally, the bridgeboard 200may be a conventional printed circuit board with variouselectrical/electronic components and connectors mounted thereon. Thebridgeboard 200 has a connector 205 that is connectible to themotherboard 100 and a connector 210 that is connectible to the externaldevice 110. The connectors 205, 210 may be conventional edge connectors,or as discussed in more detail in conjunction with FIGS. 8A, 8B, 9, and10 may include alignment mechanisms to facilitate positioning andcoupling the bridgeboard 200 with the external device 110 and/or themotherboard 100. The bridgeboard 200 also comprises electricalconnections (not shown) from the connector 205 to the connector 210through a bridge chip 215. The electrical connections may take the formof conventional tracings formed in a printed circuit board. While thepresent embodiment discloses the bridge chip 125, the functionality ofthe bridge chip 125 may be implemented in a plurality of chips in anysuitable configuration. As presented previously, the bridge chip 215creates a bridge between the environment of the motherboard 100 and theenvironment of the external device 110 without taxing performance ofeither the motherboard 100 or the external device 110. The bridgeboard200 further includes an electrically-conductive backplate 220 and anEMI-shielding gasket 225 to protect the components in the chassis fromthe elements and for containing EMI. The backplate 220 may be integrallyformed with the bridgeboard 200 or may be separately formed and attachedthereto. Generally, the backplate 220 is formed from a metal layer, suchas aluminum, copper, titanium, or the like. The bridgeboard 200 furthercomprises other elements, both electrical and mechanical, as requiredfor efficient communication between the motherboard 100 and the externaldevice 110.

[0032] As will be appreciated by one skilled in the art, it is desirablefor the motherboard 100 and the external device 110 to be aligned suchthat, when they are interconnected with the bridgeboard 200, a minimumamount of stress is applied to the interconnections between themotherboard 100, the bridgeboard 200, and the external device 110. Oneaspect of the present invention addresses this situation by preciselylocating the external device 110 with respect to the motherboard 100 andby providing an adaptable connection between the bridgeboard 200 and theexternal device 110. It is within the scope of the present invention,however, to provide an adaptable connection between either themotherboard 100 and the bridgeboard 200, between the bridgeboard 200 andthe external device 110, or both.

[0033] Various industry standards (e.g., the multi-company WTX standardand the Intel® ATX standard) specify a datum structure for placement ofelectronic and mechanical components within a chassis based upon a holein the motherboard (known as the 0,0 hole) and a surface of themotherboard. Referring now to FIG. 3, such a motherboard 300 is shownhaving a hole 305 and a top surface 310. In this example, all othercomponents in the chassis are placed in reference to the hole 305 andthe top surface 310 of the motherboard 300. FIG. 4 illustrates thisdatum structure. The top surface 310 of the motherboard 300 correspondsto datum plane A. A plane perpendicular to datum plane A and containinga centerline 400 of the hole 305 is datum plane B. A plane perpendicularto datum plane B and containing the centerline 400 of the hole 305 isdatum plane C. Locating other components within the chassis with respectto the datum planes A, B, and C fully describe the location andorientation of the other components in six degrees of freedom.

[0034] The present invention interconnects at least two electroniccomponents in at least two chassis. Not only is it desirable for the twochassis (and thus the two electronic components) to have a fixedrelationship between each other, but it is desirable for the two chassis(and thus the two electronic components) to be in a particularrelationship to one another, so that the motherboard 100 and externaldevice 110 can physically be interconnected with the bridgeboard 200 andso that a minimum amount of stress is placed upon the bridgeboard 200when it is interconnected with the motherboard 100 and the externaldevice 110.

[0035] With this in mind, attention is drawn to FIG. 5, whichillustrates an embodiment of the present invention having afixed-position motherboard 510, a rigid bridgeboard 200 that ispositioned based upon the location of the motherboard 510, and anexternal device 700 (FIG. 7) that is positioned based upon the locationof the bridgeboard 200. A primary chassis 500 has installed therein themotherboard 510 and corresponds to a populated chassis assembly. Theprimary chassis 500 has an opening 512 so that a connector 513 on themotherboard 510 is exposed. The motherboard 510 has a datum hole 515,which corresponds to the 0,0 hole of the specifications referencedabove. The motherboard 510 is located at a known location within theprimary chassis 500. The motherboard 510 specifically has a knownpositional relationship to a side wall 520 and a lower wall 525 of theprimary chassis 500. In the illustrated embodiment, the datum hole 515is mimicked or replicated in the side wall 520 of the primary chassis500 as hole 530. Thus, the hole 530 has a known relationship withrespect to the side wall 520 and the lower wall 525.

[0036] A secondary chassis 505 has an opening 535 formed in a lower wall550. The secondary chassis 505 also has a pin 545 extending from theside wall 540 in a location corresponding to the hole 530. In otherwords, the pin 545 is the same distance from the lower wall 550 as thehole 530 is from the lower wall 525. Further, the pin 545 is the samedistance from an end wall 555 as the hole 530 is from an end wall 560.Thus, the pin 545 is in a location that is a mirror image to that of thehole 530. The diameter of the hole 530 is slightly larger than thediameter of the pin 545 such that the pin 545 has a close, sliding fitinto the hole 530.

[0037] With the pin 545 inserted into the hole 530, and with the sidewall 540 against the side wall 520, the secondary chassis 505 is locatedwith respect to the primary chassis 500 in five of the six degrees offreedom: the secondary chassis 505 can rotate about a centerline throughthe pin 545 and the hole 530. To constrain this final degree of freedom,a slot 565 is provided in the side wall 520 of the primary chassis 500.A major axis 570 of the slot 565 is aligned such that, when extended, itpasses through the center of the hole 530. A pin 575 is provided in theside wall 540 of the secondary chassis 505, such that when the pin 545is inserted into the hole 530 and the side wall 540 is adjacent the sidewall 520, the pin 575 can inserted into the slot 565, resulting in theprimary chassis 500 being generally aligned with the secondary chassis505. The minor dimension of the slot (perpendicular to the major axis570) is only slightly larger than the diameter of the pin 575 such thatthe pin has a close, sliding fit into the slot 565. The pin 575 can, inan alternate embodiment, be a fastener so that, when installed, the sidewall 540 is held against the side wall 520. In the illustratedembodiment, the slot 565 is elongated, rather than round, to accommodatetolerance buildups in the manufacturing process. Holes 580 (only onelabeled) in the side wall 520 of the primary chassis 500 and holes 585(only one labeled) in the side wall 540 of the secondary chassis 505 areprovided so that fasteners (not shown) can be inserted therethrough forattaching the primary chassis 500 to the secondary chassis 505. Thus,the secondary chassis 505 is located in a predetermined relationship tothe motherboard 510.

[0038] With the primary chassis 500 attached to the secondary chassis505, as discussed above and illustrated in FIG. 6, the openings 512 and535 (shown in FIG. 5) are generally aligned to form an opening 600 intothe chassis 500 and 505. The connector 513 of the motherboard 510 (FIG.5) is exposed. The bridgeboard 200 can now be installed onto theconnector 513, which defines the location of the bridgeboard 200. Thebridgeboard 200 is provided with oversized holes 605 (only one labeled)so that the bridgeboard can be attached to the lower wall 525 of theprimary chassis 500 and the lower wall 550 of the secondary chassis 505via fasteners (not shown) through holes 610 (only one labeled) in thelower wall 525 and the lower wall 550. The holes 605 are oversized sothat the bridgeboard 200 can be installed under a minimum installationstress. In other words, the bridgeboard 200 can be installed so that theconnector 205 (FIG. 2) on the bridgeboard 200 can be connected with theconnector 513 (FIG. 5) on the motherboard 510 without creatingunacceptable stress in either the motherboard 510 or the bridgeboard200. The bridgeboard 200 can be attached to the primary and secondarychassis 500 and 505 by any desired way suitable for the application,such as with screws, nuts and bolts, rivets, push-through connectors,and the like. With the bridgeboard 200 thus installed, the primary andsecondary chassis 500 and 505, in combination with the backplate 220(FIG. 2) and the EMI-shielding gasket 225 (FIG. 2) of the bridgeboard200, provide a barrier against emissions of electromagnetic waves fromthe computer system.

[0039] Turning now to FIG. 7, the external device 700 can now beinstalled into an interior portion of the secondary chassis 505 andinterconnected with the bridgeboard 200. As it is being installed, theexternal device 700 is guided along rails 702 on the inside of thesecondary chassis 505. The rails 702 are positioned with respect to theside wall 540 of the secondary chassis 505, which sets a spacing fromthe connector 820 (FIG. 8) on the external device to the connector 210(FIGS. 2, 8) on the bridgeboard 200 when the connectors 820, 210 areconnected. The external device 700 is not precisely located by the rails702 but rather is allowed to “float” to a degree between the rails 702.For example, the distance between adjacent rails 702 may be greater thanthe thickness of the external device 700, thereby allowing the externaldevice 700 to move from side-to-side between adjacent rails 702. Inother words, adjacent rails 702 do not firmly or rigidly hold theexternal device 700 but rather guide its location within a fixeddimension. Now with attention to FIG. 8A, as a leading edge 705 of theexternal device 700 nears the connector 210, a locating pin 800 on theconnector 210 enters a corresponding opening 810 in a locating block 820attached to the external device 700. The pin 800 has a chamfered portion830 to assist in guiding the pin 800 into the opening 810. Thus, as thelocating pin 800 enters the opening 810 (FIG. 8B), the external device700 is located with respect to the connector 210, and the externaldevice 700 can be interconnected with the bridgeboard 200 with littleremaining stress on the bridgeboard 200 or the external device 700. Theexternal device 700 can now be rigidly affixed to the secondary chassis505.

[0040] In one embodiment of the present invention, a method of datumsharing is provided including determining a position and orientation ofthe motherboard 300, 510 and defining at least one datum feature in theprimary chassis 500 describing the position and orientation of themotherboard 300, 510. In one embodiment, the position and orientation ofthe motherboard 300, 510 is determined by determining the first plane A(FIG. 4) corresponding to the surface 310 of the motherboard 300, 510, asecond plane B (FIG. 4) perpendicular to the surface 310 of themotherboard 300, 510 having a center of the hole 310, 515 in themotherboard 300 thereon, and a third plane C (FIG. 4) perpendicular tothe second plane B and having the center of the hole 310, 515 in themotherboard 300 thereon. In one embodiment, defining at least one datumfeature in the primary chassis 500 further comprises defining a wall 520in the primary chassis 500 parallel to the first plane A, defining ahole 530 in the wall 520 having a center corresponding the center of thehole 305, 515 in the motherboard, and defining a slot 565 in the wall520, wherein a major axis 570 of the slot 565 lies on the second planeB. The method further comprises defining at least one datum feature inthe secondary chassis 505 corresponding to the at least one datumfeature in the primary chassis 500. In one embodiment, defining at leastone datum feature in the secondary chassis 505 further comprisesdefining a wall 540 in the secondary chassis 505 parallel to the wall520 of the primary chassis, defining a pin 545 extending outwardly fromthe wall 540 corresponding to the hole 530 in the wall 520 of theprimary chassis 500, and defining a pin 575 extending outwardly from thewall 540 corresponding to the slot 565 in the wall 520 of the primarychassis 500. Alternatively, the pin 575 may be a fastener.

[0041] In another embodiment, a method for datum sharing is providedincluding defining the datum structure for the motherboard 510 andtransferring the datum structure to the primary chassis 500 to define arelationship between a location and orientation of the motherboard 510and a location and orientation of the primary chassis 500. Further, themethod includes transferring the datum structure to the secondarychassis 505 to define a relationship between the location andorientation of the primary chassis 500 and the location and orientationof the secondary chassis 505. In one embodiment, the method furthercomprises locating an external device 700 in the secondary chassis 505based upon the datum structure transferred to the secondary chassis 505.

[0042]FIG. 9 illustrates an embodiment of the present invention in whicha main portion 900 of a device (corresponding to either a motherboard oran external device) is in a fixed relationship to the chassis 905 viaone or more standoffs 910 (one shown) attached to a side wall 915 of thechassis 905. Further, the bridgeboard 920 is in a fixed relationship tothe chassis 905 and is attached via standoffs 922 (one shown) to thebackplate 923. The main portion 900 is electrically interconnected via aflexible circuit 925, containing electrical conductors for each of thelines to be connected, to an electrical connector 930. The electricalconnector 930 can be a conventional edge connector or any other type ofconnector suitable for the application. Attached to the electricalconnector 930 is a guide block 935 that may be made of any suitablematerial, e.g., Teflon™, Delrin™, or the like. The guide block 935 has arecess 940 therethrough that is adapted to slidably receive a guide pin945, which is affixed to the side wall 915 of the chassis 905. Thus, inthis embodiment, the connector 930 and the guide block 935 are capableof moving as indicated by double-headed arrow 950. Accordingly, theconnector 930 and the guide block 935 move, as indicated by thedouble-headed arrow 950, to seek the lowest-stress condition as theconnector 930 is interconnected with the connector 955. Further, in thisembodiment, a gasket 960 is provided for sealing from the elements andfor EMI containment.

[0043] In the embodiment illustrated in FIG. 10, a device 1000(corresponding to either a motherboard or an external device) is in afixed relationship with the chassis 1005 via a standoff 1010 that isattached to a side wall 1015 of the chassis 1005. A main portion 1020 ofthe bridgeboard 1025, as well as a backplate 1030 attached to thebridgeboard 1025, is in a fixed relationship to the chassis 1005. Themain portion 1020 is electrically attached to a connector 1035 via aflexible circuit 1040, containing electrical conductors for each of thelines to be connected, and a connector board 1045. The connector 1035 isphysically attached to the connector board 1045, as is a guide block1050 that may be made of any suitable material, e.g., Teflon™, Delrin™,or the like. The guide block 1050 has a recess 1055 therethrough that isadapted to receive a guide pin 1060, which is attached to a wall 1065 ofthe backplate 1030. The guide pin 1060 thus guides the guide block 1050,the connector board 1045, and the connector 1035 in a directioncorresponding to the double-headed arrow 1070. Thus, the guide block1050, the connector board 1045, and the connector 1035 move in adirection corresponding to the double-headed arrow 1070 to seek thelowest stress condition as a connector portion 1075 of the device 1015is mated with the connector 1035. Further, in this embodiment, a gasket1080 is provided for sealing from the elements and for EMI containment.The illustrated embodiment also provides a stop block 1085 to providesupport for the connector plate 1045.

[0044] The scope of the present invention includes any of theembodiments illustrated in FIGS. 8A, 8B, 9, and 10 used in anycombination on either or both of the primary device or motherboard andthe external device.

[0045] Referring again to FIGS. 5-8B, the computer system according tothe illustrated embodiment is assembled by first attaching themotherboard 510 to an interior portion of the primary chassis 500. Theprimary chassis 500 is positioned such that the side wall 520 is facingup and the secondary chassis 505 is placed onto the primary chassis 500such that the pin 545 enters the hole 530 and the pin 575 enters theslot 565. Thus, the secondary chassis 505 is generally aligned with theprimary chassis and the openings 512 and 535 are generally aligned.Fasteners (not shown) are installed through the holes 580 and 585 (onlyone of each labeled) to hold the two chassis 500 and 505 together. Thebridgeboard 200 is installed such that the connector 205 is mated withthe motherboard connector 513 and the bridgeboard 200 is attached to theprimary chassis 500 and the secondary chassis 505. The bridgeboard 200is attached to at least one of the primary chassis 500 and the secondarychassis 505 to position the bridgeboard 200 and to shield the openings512 and 535 to inhibit electromagnetic waves from escaping from theinterior portion of the primary chassis 500 and the secondary chassis505. The assembly is then rotated such that the bridgeboard 200 is onthe bottom and the external device 700 is installed. The external device700 is guided along the rails 702 and is located with respect to theconnector 210 on the bridgeboard 200 by the locating pin 800 and theopening 810. As the external device 700 is located, it is bothphysically and electrically interconnected with the connector 210 on thebridgeboard 200. The external device 700 can now be rigidly affixed tothe secondary chassis 505. Thus, when the secondary chassis 505 isattached to the primary chassis 500 and the external device 700 isinstalled, the external device 700 is located in a predeterminedrelationship to the motherboard 510 and in a predetermined volume in theinterior portion of the secondary chassis 505.

[0046] In the embodiments illustrated in FIGS. 9 and 10, the primarychassis 500 and the secondary chassis 505 (FIG. 5) may be attached toone another and populated in any desired order, as the interconnectionbetween the bridgeboard 920, 1025 and the device 900, 1000 is made viathe flexible circuit 925, 1040. In one embodiment, the secondary chassis505 is attached to the primary chassis 500 (FIG. 5). Referring inparticular to FIG. 9, the main portion 900 of the device is attached tothe interior portion of the side wall 915 of the chassis 905. Theposition of the electrical connector 930 is adjusted to generally alignthe electrical connector 930 and the electrical connector 955 beforeelectrical connector 930 and the electrical connector 955 are connected.In the illustrated embodiment, the main portion 900 and connector 930can be that of the motherboard 510 (FIG. 5) or the external device 700(FIG. 7). Referring now to FIG. 10, the device 1000 is attached to theinterior portion of the side wall 1015 of the chassis 1005. The positionof the electrical connector 1035 is adjusted to generally align theconnector 1075 with the connector 1035 before electrical connector 1075and the electrical connector 1035 are connected. In the illustratedembodiment, the connector 1035 can be the connector 205 or the connector210 on the bridgeboard 200 (FIG. 2) that mates with the connector 513 ofthe motherboard 510 (FIG. 5) or the connector 820 of the external device700 (FIG. 8).

[0047] The present invention further encompasses an apparatus havingmeans for performing certain embodiments of the method of the inventiondescribed herein and their equivalents.

[0048] The particular embodiments disclosed above are illustrative only,as the invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood as referring to the power set (the set of all subsets) of therespective range of values, in the sense of Georg Cantor. Accordingly,the protection sought herein is as set forth in the claims below.

What is claimed is:
 1. A modular computer system, comprising: a primarychassis having a first opening; a motherboard disposed in the primarychassis, wherein the motherboard has an electrical connector disposedbehind the first opening; a secondary chassis attached to the primarychassis and having a second opening, wherein the first opening and thesecond opening are generally aligned; an external device disposed in thesecondary chassis, wherein the external device has an electricalconnector disposed behind the second opening; a bridgeboard having afirst electrical connector interconnected with the motherboardelectrical connector and a second electrical connector interconnectedwith the external device connector, wherein the bridgeboard is disposedwithin the first opening and second opening; and a backplate coveringthe first opening and second opening.
 2. A modular computer system,according to claim 1, wherein the backplate is made of an electricallyconductive material.
 3. A modular computer system, according to claim 1,wherein the backplate is integral with the bridgeboard.
 4. A modularcomputer system, according to claim 1, wherein the bridgeboard isattached to the backplate.
 5. A modular computer system, according toclaim 1, wherein the motherboard is located in a predetermined positionin the primary chassis.
 6. A modular computer system, according to claim1, wherein a location of the bridgeboard with respect to the primarychassis and the secondary chassis is determined by a location of themotherboard in the primary chassis.
 7. A modular computer system,according to claim 3, wherein a location of the external device in thesecondary chassis is determined by the location of the bridgeboard.
 8. Amodular computer system, according to claim 1, further comprising agasket between the backplate and the primary chassis and between thebackplate and the secondary chassis.
 9. A modular computer system,according to claim 1, wherein the backplate is attachable to the primarychassis and the secondary chassis based upon a location of themotherboard in the primary chassis.
 10. A modular computer system,according to claim 1, wherein the primary chassis has at least oneattachment hole, the secondary chassis has at least one attachment hole,and the backplate has at least two attachment holes, wherein theattachment holes are for receiving fasteners therethrough to attach thebackplate to the primary chassis and the secondary chassis, wherein theat least two attachment holes in the backplate are larger than the atleast one hole in the primary chassis and the at least one hole in thesecondary chassis.
 11. A modular computer system, according to claim 1,wherein each of the primary chassis and the secondary chassis have aplurality of attachment holes therethrough for receiving fastenerstherethough to attach the primary chassis to the secondary chassis. 12.A modular computer system, according to claim 1, further comprising aplurality of rails in the secondary chassis for guiding the location ofthe external device within a predetermined volume.
 13. A modularcomputer system, according to claim 12, wherein the plurality of railsare sufficiently spaced to allow the external device to moveside-to-side between adjacent rails.
 14. A modular computer system,according to claim 1, wherein the bridgeboard further comprises alocating pin and the external device further comprises a locating blockhaving a recess therein adapted to receive the locating pin.
 15. Amodular computer system, according to claim 14, wherein the locating pinhas a chamfered portion to assist in guiding the locating pin into therecess.
 16. A modular computer system, according to claim 1, wherein themotherboard further comprises a main portion and a flexible circuitinterconnecting the main portion and the motherboard electricalconnector, the modular computer system further comprising: a guide pinattached to the primary chassis; and a guide block having a recesstherethrough and attached to the motherboard electrical connector,wherein the recess is adapted to receive the guide pin so that the guideblock is capable of sliding along the guide pin.
 17. A modular computersystem, according to claim 1, wherein the external device furthercomprises a main portion and a flexible circuit interconnecting the mainportion and the external device electrical connector, the modularcomputer system further comprising: a guide pin attached to the primarychassis; and a guide block having a recess therethrough and attached tothe motherboard electrical connector, wherein the recess is adapted toreceive the guide pin so that the guide block is capable of slidingalong the guide pin.
 18. A modular computer system, according to claim1, wherein the bridgeboard further comprises a main portion, a connectorboard, and a flexible circuit, wherein the main portion and theconnector board are interconnected via the flexible circuit and thefirst connector is electrically connected to the connector board, themodular computer system further comprising: a guide pin attached to thesecondary chassis; and a guide block having a recess therethrough andattached to the connector board, wherein the recess is adapted toreceive the guide pin so that the guide block is capable of slidingalong the guide pin.
 19. A modular computer system, according to claim18, further comprising a stop block disposed between the connector boardand the backplate and attached to the backplate to support the connectorboard, wherein the connector board is capable of sliding along a surfaceof the stop block.
 20. A modular computer system, according to claim 1,wherein the bridgeboard further comprises a main portion, a connectorboard, and a flexible circuit, wherein the main portion and theconnector board are interconnected via the flexible circuit and thesecond connector is electrically connected to the connector board, themodular computer system further comprising: a guide pin attached to thesecondary chassis; and a guide block having a recess therethrough andattached to the connector board, wherein the recess is adapted toreceive the guide pin so that the guide block is capable of slidingalong the guide pin.
 21. A modular computer system, according to claim20, further comprising a stop block disposed between the connector boardand the backplate and attached to the backplate to support the connectorboard, wherein the connector board is capable of sliding along a surfaceof the stop block.
 22. An apparatus for electrically interconnecting afirst device with a second device, wherein the first device is attachedto a structure, the apparatus comprising: a first connector; a flexiblecircuit electrically connected to the first device and the firstconnector; a second connector electrically connected to the seconddevice; a guide pin attached to the structure; and a guide block havinga recess therethrough and attached to the first connector, wherein therecess is adapted to receive the guide pin so that the guide block iscapable of sliding along the guide pin.
 23. An apparatus forelectrically interconnecting a first device with a second device,wherein the second device is attached to a structure, the apparatuscomprising: a first connector electrically connected to the firstdevice; a second connector; a connector board attached to andelectrically connected to the second connector; a flexible circuitelectrically connected to the second device and the connector board; aguide pin attached to the structure; and a guide block having a recesstherethrough and attached to the connector board, wherein the recess isadapted to receive the guide pin so that the guide block is capable ofsliding along the guide pin.
 24. An apparatus, according to claim 23,further comprising a stop block disposed between the connector board andthe structure and attached to the structure to support the connectorboard, wherein the connector board is capable of sliding along a surfaceof the stop block.
 25. An apparatus, comprising: a primary chassishaving a first opening; a secondary chassis attached to the primarychassis and having a second opening, wherein the first opening and thesecond opening are generally aligned; and a backplate covering the firstopening and second opening.
 26. An apparatus, according to claim 25,wherein the backplate is made of an electrically conductive material.27. An apparatus, according to claim 25, further comprising a gasketbetween the backplate and the primary chassis and between the backplateand the secondary chassis.
 28. An apparatus, according to claim 27,wherein the gasket is an electromagnetic interference-shielding gasket.29. An apparatus, according to claim 25, wherein the primary chassis hasat least one attachment hole, the secondary chassis has at least oneattachment hole, and the backplate has at least two attachment holes,wherein the attachment holes are for receiving fasteners therethrough toattach the backplate to the primary chassis and the secondary chassis,wherein the at least two attachment holes in the backplate are largerthan the at least one hole in the primary chassis and the at least onehole in the secondary chassis.
 30. An apparatus, according to claim 25,wherein each of the primary chassis and the secondary chassis have aplurality of attachment holes therethrough for receiving fastenerstherethough to attach the primary chassis to the secondary chassis.